Non-polluting by-product coal carbonization plant

ABSTRACT

As coal is heated to produce coke and coke oven gas the coke is delivered to a reactor where a bed of it is maintained. Most of the tar and ammonia and oil are removed from the coke oven gas and then the gas is passed through the coke bed. A tar plant receives the tar removed from the gas and produces coal tar pitch, which is delivered with calcium carbonate to the reactor to desulfurize the coke and gas therein and enriches the gas. The desulfurized gas is continuously removed from the reactor and cooled. Periodically a batch of desulfurized coke is withdrawn from the reactor. Steam is produced in cooling the coke and is used in heating an ammonia still. Water from the still is processed and used in an ammonia scrubber along with make-up water produced by condensing water vapor from the coke oven combustion gas. Only nonpolluting products leave the system. The rest are consumed or recirculated in it.

United States Patent Kelmar [451 May 9, 1972 [54] NON-POLLUTING BY-PRODUCT COAL C ARBONIZATION PLANT Primary Examiner-Norman Yudkofi Assistant Examiner-David Edwards [72] Inventor: John J. Kelmar, 2205 Cypress Drive, Anomey gmwn, Murray Flick & peckham White Oak, McKeesport, Pa. 15131 221 Filed: on. 28, 1970 [571 ABSTRACT [21] APP] No: 84,551 As coal is heated to produce coke and coke oven gas the coke is delivered to a reactor where a bed of it is maintained. Most of the tar and ammonia and oil are removed from the coke [52] 11.5. C1. ..20l/17, 201/20, 201/23, oven gas and then the gas is passed through the coke bed. A 201/30, 202/109, 202/226, 23/2099, 23/181 tar plant receives the tar removed from the gas and produces 1] Int, Cl, ,,Cb 57/06 coal tar pitch, which is delivered with calcium carbonate to 53 Field (Search 17 2 23,29,30; the reactor to desulfurize the coke and gas therein and en- 202/109, 226; 23/2099. 181; 203/89 riches the gas. The desulfurized gas is continuously removed from the reactor and cooled. Periodically a batch of desul- [56] References Cited furized coke is withdrawn from the reactor. Steam is produced in cooling the coke and is used in heating an ammonia still. UNlTED STATES PATENTS Water from the still is processed and used in an ammonia scrubber along with make-up water produced by condensing 3'481'834 12/1969 Squ'res "201/17 water vapor from the coke oven combustion gas. Only nonpol- 3'451'896 6/1969 201/27 luting products leave the system. The rest are consumed or 2,824,047 2/1958 Gorm et a1. ..201/17 recirculated in it 2,649,403 8/1953 Eaton ...201/3O X 1,545,620 7/1925 Trent ..201/1 7 UX 13 Claims, 2 Drawing Figures WWiE/l/ PLANT I I I l l l l II I I} k0 JAUME 44 a i 5 2 4 a0 a5 a6 7 Q 32 73 9 COKE 2 56 77 flVE/V 3 66 C Ol/E/VGA 84 ms s 74 Q 24 27 g 5 23 E /0/ 2e 75 $754M yea/0:0 as l 1 L u 1 t 93 00 6A5 0/Z COX/051157175 PATENTEDMAY 91972 3,661,719

sum 1 BF 2 OXVGf/V PLANT 2/ C02 +h' 0 144m C OKE OVEN 6A3 O/A C OA/DEA/SATE l/VVE/VTO P1 1 JOHN J. 44-24445 ATTORNEYS.

PATENTEDMAY 9|972 I 3,661,719

sum 2 BF 2 CARBON D/OX/DE FLA/V7 COKE OVA-W645 L lQU/D UREA PLANT GAS OIL CONDENSA 75 2 By JOHN J. 42231;-

ATTORA/EKS.

NON-POLLUTING BY-PRODUCT COAL CARBONIZATION PLANT Air pollution from the coke industry has become very serious. In the carbonization of coal in by-product coke ovens a large amount of coke oven gas, tar, light oils and various coal chemicals are produced. There is a problem of safely disposing of the by-products that cannot be used, and of getting rid of the coke oven gas not needed in the plant. It is not suitable for pipe line gas because of its sulfur, moisture and tar compounds content. Also, a huge amount of air is required in the carbonization process and after the oxygen is burned out of the air the remainder becomes a pollutant, along with the other products of combustion.

Another serious source of pollution comes from quenching hot coke with water, which generates a large volume of steam contaminated with sulfur oxide and sulfuric acid. The quenching water that is not evaporated contains sulfur, weak ammonia liquor, sodium sulfate solutions, and solutions containing phenols and tars, so it cannot be discharged into rivers. Therefore, it is recirculated until all of it is evaporated into steam, but the steam is highly contaminated.

it is among the objects of this invention to provide a method and apparatus for carbonizing coal, which does not pollute the atmosphere or water resources, which desulfurizes the hot coke, which purifies and enriches the coke oven gas, and which safely takes care of the chemical wastes.

The invention is illustrated in the accompanying drawing, which FIGS. 1 and 2 are a diagram of my by-product coal carbonization apparatus.

Referring to the drawing, coal is crushed and screened in suitable apparatus 1 and then charged into a coke oven 2 having a combustion chamber 3. After the coal is heated in the oven and carbonized into coke, the hot coke is pushed into a closed conveyor hopper 4 and onto a covered conveyor 5 that delivers it to the top of a closed hopper 6. This hopper is separated from a lock hopper 7 below it by means of an electrically controlled valve 8. The bottom of the lock hopper likewise normally is closed by an electric valve 9 at the top ofa tall reactor 10. The coke filling the lock hopper is emptied into the reactor when valve 9 is opened while the valve above it is closed. Then valve 9 is closed and the upper valve is opened to fill the lock hopper from the open hopper above it. The gas pressure due to coke movement in the lock hopper and the reactor hopper is equalized by a pipe 11 connecting them and provided with a relief valve. The two hoppers and the reactor are surrounded by water jackets 12, and the steam generated in these jackets by the hot coke is delivered by conduits l3, l4 and 15 to a steam drum 16. The drum also receives steam through a conduit 17 from a waste heat boiler 18 that is heated by the products of combustion from the coke oven combustion chamber.

The bottom of the reactor is provided with a normally closed electric valve 21 that opens into a lower lock hopper 22 separated from a discharge hopper 23 by another electrically operated valve 24. The bottom of the discharge hopper has an electric valve 25, through which coke can be discharged into a conveyor 26 that carries it away to storage. The two lower hoppers are surrounded by water jackets 27, to which chilled water is delivered through a conduit 28 and from which warm water leaves the jackets through another conduit 29. These two conduits are connected to the opposite ends of a refrigerator coil 30 that is cooled in a manner that will be described later. The temperature of the coke in hopper 22 is reduced from about l,000 F. to about 500 F., and it is further reduced in the discharge hopper 23 to about 100 F. for the conveyor. A relief valve 31 equalizes the pressure in the reactor and lower lock hopper when coke moves into the latter.

The hot coke in the reactor is completely carbonized and contains a predominating proportion of the element carbon and a comparatively small proportion of the elements oxygen and hydrogen, residual ash and sulfur. It contains no volatile matter and is considered to be a material with high activation properties. Most active carbon is produced at temperatures of l,500 F. to l,600 F. These high temperatures in the reactor result in high reaction.

The gases and vapors that leave the coke oven are processed for coal chemicals. The first step is the recovery of the basic crude materials, which are coke oven gas, ammonia liquor, tar and light oil. The gases and vapors leaving the oven are cooled by spraying with flushing liquor in a collecting main 32. This liquor provides a carrying medium for the condensable tars and other compounds formed in the operation. The tars and ammonia are separated from the flushing liquor by processing it through a flushing liquor decanter 33, from which the tar flows through a line 34 into a tar separator 35 and then a storage tank 37. The flushing liquor from the decanter flows through a line 36 into a circulating tank 38, from which a pump 39 delivers it to a weak ammonia liquor tank 40 where the ammonia liquor is separated. Then the flushing liquor, free from most of the tars and ammonia, is recycled back through a line 41 to the collector main 32 for cooling the coke oven crude gas.

The non-condensed coke oven gas leaving the collector main through a line 44 flows through a water cooled primary cooler 45, but the condensate of liquor and tar flows from the cooler through a line 46 to a primary cooler decanter 47. The flushing liquor flows through a line 48 into the flushing liquor decanter 33 and the tar is delivered to the tar separator 35. The gas from the primary cooler is pumped by an exhauster 49 into an electrostatic precipitator tar extractor 50, from which the tar flows through a line 51 to the tar separator while the tar-free gas is pumped through a line 52 into ammonia scrubbers 53, where it is washed in countercurrent stages operating in series, first with a weak ammonia solution from line 54 and finally with purified water obtained through a line 55 from a reverse osmosis system 56 that will be explained later. The ammonia liquor from the scrubbers is delivered through a line 57 to the tank 40. I

The coke oven gas, free of ammonia, flows from the scrubbers through a line 60 to a light oil scrubber 61, where about 95 per cent of the oil in the gas is removed. This oil from this scrubber is circulated through a light oil still 62 and is collected in a storage tank 63. The oil-scrubbed gas is pumped by a booster station 64 through a line 65 to a manifold bustle pipe 66 encircling the lower part of the reactor and provided with a number of tuyeres 67 leading into the reactor so that the gas is forced up through the bed of hot coke therein and out through a take-off pipe 68 near the upper end of the reactor.

About 40 per cent of the sulfur in the coal, not removed in the coal cleaning process, is evolved in the distillation products. Much of this remains in the coke oven gas, generally in the form of hydrogen sulfide. This is removed as the gas passes through the reactor, as will be explained presently.

From the tar storage tank 36 the tars are delivered to a tar plant 70 that receives some sulfuric acid, tar-containing oil from a benzene plant, carbon dioxide from a lime kiln 71 and caustic soda from a causticizer 72. The products of the tar plant are mainly oils, creosote, naphthaline and tar acids, which have value. The coal tar residue and other waste materi als, sodium sulfate, phenols etc. produced in the tar plant are delivered to a mixing hopper 73 through a line 74 carrying coal tar pitch (no longer used to any great extent as fuel for open hearth furnaces), a second line 75 carrying sodium sulfate sludge, to which is added calcium carbonate sludge from the causticizer. This material, combined in the mixing hopper, is atomized by steam from a line 76 from the steam drum l6 and sprayed into the reactor through spray nozzles 77 in its top. The sprayed material desulfurizes the coke and coke oven gas in the reactor and enriches the gas to make it suitable for pipeline gas. The impurities are removed.

The calcium carbonate sludge injected into the reactor from the causticizer is decomposed into C80 and CO In the presence of hot coke, carbon dioxide is reduced by this reaction: C0 C 2C0 at temperature of l,700 F. Below this temperature excess CO will probably produce this reaction: 4CO Ca S= 4CO+ Ca 50,. The lime will react with the sulfur compounds in the coke oven gas in the form of hydrogen sulfide, carbonly sulfide and carbon disulfide.

The amount of lime generated in the reactor from the injected sludge is very much above the stoichmetric requirements for neutralizing the sulfur in the coke oven gas. The excess lime desulfurizes the coke, in which the sulfur exists in four forms: ferrous sulfide, sulfates, free absorbed sulfur and solid solution of sulfur with carbon. The desulfurization by lime causes a portion of the ferrous sulfide formed by sulfur combining with iron in the ash in the reactor to be converted to calcium sulfide as seen by this equation: FeS Ca C =CaS Fe CO. This reaction occurs in the temperature range of 1,600 F. The free sulfur in the coke will be converted to hydrogen sulfide in the reactor. The hydrogen units sulfur according to the following reaction: H S H 8. Organic sulfur and sulfur with carbon will undergo these reactions:

450 4 G 3CaSO CaS CS 2H C+ 2H S The hydrogen sulfide (H 8) will react to form calcium sulfide, so the sulfur in the coke leaving the reactor will be mainly in the form of compounds of calcium sulfide and calcium sulfate. Since the sulfur has been removed from the surface of the coke by lime and steam, this coke charged into the blast furnace will not contaminate the lime in the furnace; and therefore that lime will be in much better condition to desulfurize the iron in the blast furnace. Furthermore, in the blast furnace in the presence of an oxidizing flame, most of the sulfur in the coke, in form of sulfides and sulfates, will go into the slag without being first chemically transferred into the metal, thus resulting in a decrease in the amount of limestone charged into the blast furnace.

As the tar pitch is sprayed onto the hot coke, the tar constituents undergo endothermic chemical decomposition or cracking, which produces interallied components of carbon and hydrogen. These molecular fragments form gases that enter the coke oven gas stream and add about 150 B.T.U.'s of calorific value to each cubic foot of coke oven gas. Additional enrichment of the gas also comes from cracking of the light oil brought into the reactor by the coke oven gas. The enriched gas, heated by flowing up through the coke bed, releases most of its heat in a waste heat boiler 80, through which it flows from take-off pipe 68, and then it is cooled in a heat exchanger 81 and a gas cooler 82. The waste heat boiler 80 produces steam that is led through a pipe 83 to the steam drum. The heat exchanger and the gas cooler receive chilled water through lines 84 and 85, from the lower end of the refrigerator and return warm water toits upper end through lines 86 and 87. A collecting line 88 for any oil condensate that may form as the gas is being cooled in waste heat boiler 80, heat exchanger 81 and cooler 82 returns the oil to the light oil still 62.

A high quantity of heat removal is required to reduce the temperature of the coke in the reactor from 1,800 to 1,000" F which is below the ignition point of coke. This is accomplished by the coke oven gas flowing up through the coke bed, by the spraying of the bed with the cold alkali sludge, and by endothermic reactions of gas balancing exothermic methane gas formation.

The gas leaving the cooler 82 passes through a booster station 90 where it is pumped to a regulator 91. Most of the gas, having a calorific value of approximately 700 B.T.U. per cubic foot, leaves the regulator through a pipe line 92 for commercial use, but some of it is returned by a line 93 to the coke oven combustion chamber where it is burned with substantially pure oxygen to form the fuel for heating the coke oven. The temperature of the fuel combustion flame is controlled by steam delivered through a line 94 from waste heat boiler 18. The source of the oxygen will be described presently.

In a conventional coke by-product plant, about 40 per cent of the gas produced in the coke ovens is returned to the ovens for heating and carbonizing the coal. The gas is burned with .air combustion and produces a heat release of 100 B.T.U.s

per cubic foot of air used. In my method the enriched coke oven gas that is returned to the ovens is only about 20 per cent of the gas produced. This smaller quantity of returned gas arises from the following combustion improvements: (1) the enriched gas produces a higher flame temperature; (2) the gas is burned with pure oxygen so the heat is increased to 300 B.T.U. per cubic foot; and (3) the dissociation of carbon dioxide and water vapor opens the store of latent heat energy to provide an increase of thermal efficiency. The dissociation of carbon dioxide and water vapor is an endothermic reaction and controls the high temperature flame (5,000 F.) by removing energy from reacting gases by heattransfer. When the temperature drops below the dissociation temperature, the fuel elements of carbon and hydrogen again combine with oxygen to release energy and form products of completed reactions of C0 and H 0. For dissociation requirements, 40 per cent of superheated steam vapor is mixed with 60 per cent oxygen and this mixture is then used to burn the enriched cokeoven gas. An oxygen operated coke oven is less complicated to construct because the waste gases are not processed through complex auxiliary apparatus or regenerators for reclaiming heat.

Ammonia liquor from the bottom of the first ammonia scrubber is collected with a portion of the flushing liquor in storage tank 40 that serves as a feed reservoir for an ammoniadistillation column 97. The weak liquor first is pumped into a dissociator 98 for the removal of acid gases of hydrogen sulfide and carbon dioxide, which leave through a line 99 to conventional apparatus for converting the acid gases to elemental sulfur. The weak ammonia liquor is pumped through a line 96 to the top of the ammonia-distillation column, which is heated by steam delivered by a line 100 from the steam drum to drive out the ammonia. Lime for the still is delivered through a line 101 from the lime kiln 71 and a.slaker 102 to liberate fixed ammonia vapors from the liquor. The lime is produced from coke and lime stone, burned in lime kiln 71 with pure oxygen from a line 103. The slaked lime enters the fixed leg 104 of the ammonia still for decomposing fixed ammonia salts.

The ammonia liquor is dephenolized by circulating the liquor through a dephenolizing tank 105 using caustic soda delivered through a line 106 from the causticizer 72, forming sodium phenolate product leaving through outlet 107. The sludge from the ammonia still is free of ammonia but contains mainly slats of calcium chloride and calcium sulfate. This liquid is processed through the reverse osmosis system 56 for removal of the chemical salts, which can be used for dust prevention on roads and the like, or for refrigeration. The water, free of salts, is circulated by a pump 108 and the line 55 to the gas scrubber.

The anhydrous ammonia from the ammonia still 97 is partially condensed in a cooler 109 and is delivered into a holding tank 110 and is then cooled, compressed and liquefied and delivered into a liquid storage tank 111. This liquid ammonia is compressed to a higher pressure by a compressor 112 and delivered through a line 113 to a stem heated autoclave 114 for production of urea. The autoclave also receives liquid carbon dioxide from a line 115 from a sourceto be described presently. 1n the autoclave the ammonia and carbon dioxide are reacted to form ammonium carbonate. The reactants require about two hours to pass through the autoclave, which is maintained at a temperature of approximately 370 F. and a pressure of 1,500 to 3,000 psi. The yield of urea in the crude melt, based on the carbon dioxide charged, is 80 to 85 per cent. If the ammonia recovered by absorption is taken into account, the yield is essentially the same, based on the ammonia charged. However, about 60 per cent of the crude urea is recovered as crystalline product, the remainder going to make up liquid fertilizer having a high nitrogen content of about 46 per cent.

The only appreciable products of combustion leaving the stack of the coke oven are carbon dioxide and water vapors and these are drawn off by a suction fan 12] and are delivered through a line 122 to a condenser 123 where the carbon dioxide .is separated. The condensed water vapor passes through a deaertor 124 and enters a storage tank 125, from which the purified water is delivered to the ammonia scrubbers for make up. The carbon dioxide enters a holding tank 127 that delivers carbon dioxide through a cooler 128 to a multi-stage compressor 129 connected to another cooler 130 and a condenser 131 that empties into a liquid storage tank 132. Most of the carbon dioxide from this tank is compressed to a still higher pressure by a compressor 133 and then is delivered through a line 134 to a regulator 135, from which line 115 delivers some of the liquid carbon dioxide to the urea plant.

Surplus carbon dioxide is delivered from storage tank 132 and an expansion tank 137 and then to a machine 138 for making solid carbon dioxide or dry ice. Some of the liquid carbon dioxide from compressor 133 flows through a line 139 from regulator 135 to the refrigerator coil 30 to chill the water that is used in cooling the coke in the reactor and the coke oven gas that leaves the reactor. From this coil carbon dioxide gas is returned through a line 140 to the holding tank 127, which also receives carbon dioxide gas from the tar plant through a line 141.

Liquid carbon dioxide in line 139 also is conducted by a line 143 to a carbon dioxide refrigerator 144 that forms part of a conventional air separation or oxygen plant, in which air is separated into oxygen and nitrogen. Thus, air is pumped through a compressor 145 and then any carbon dioxide and any dust present in the air are removed with a KOH solution in scrubbers 146. The air then passes through a multi-stage compressor 147, with water cooling between the stages. Any moisture that condenses out during this process is removed by passing the air through a tower 148 packed with solid KOH. After the gas leaves the last compression stage it is watercooled in a cooler 149 and further cooled by the liquid carbon dioxide in the refrigerator 144. The vaporized carbon dioxide is returned through lines 150 and 140 to the holding tank 127. The refrigerated air, on the other hand, flows through a pipe 152 to a rectifier 153 where the air is liquefied and separated into its constituents, with the nitrogen escaping into the atmosphere. The liquid oxygen from the rectifier flows into an insulated storage tank 154 connected by a pump 155 with a pipe 156 leading to the combustion chamber 3 of the coke oven and to a line 103 leading to the lime kiln 71. On the way, the liquid oxygen can be changed to its gaseous form where used Spent KOH from the air separation plant is delivered through a pipe 157 to the mixing hopper 73.

One of the big advantages of this system which makes it economically feasible, is that it utilizes the steam generated in the plant and can use a large quantity of water because the water is continually recirculated.

According to the provisions of the patent statues, I have explained the principle of my invention and have illustrated and described what 1 now consider to represent its best embodiment. However, I desire to have it understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specifically illustrated and described.

lclaim:

1. The method of carbonizing coal, comprising heating the coal in a coking chamber to produce coke and coke oven gas, forming a bed of said hot coke in a reactor, removing most of the tar and ammonia and oil from said gas in separation means and then passing the gas through said hot coke bed, producing coal tar pitch in a tar plant from said removed tar, making calcium carbonate in a causticizer, delivering said pitch and calcium carbonate to said bed to desulfurize the coke and the gas therein, continually removing the gas from the bed after the gas has passed therethrough, cooling the removed gas, and periodically withdrawing a batch of desulfurized coke from said bed.

2. The method recited in claim 1, including producing steam by waste heat from said coal heating and by heat removed from said gas in cooling it, and using said steam to spray said tar pitch and calcium carbonate onto said bed.

3. The method recited in claim 1, including using steam, substantially pure oxygen and some of said removed coke oven gas to produce the heat for the coal and form products of combustion that include carbon dioxide gas and water vapor, condensing said vapor and separating it from the carbon dioxide, liquefying the carbon dioxide, and using liquefied carbon dioxide as a refrigerant in the production of liquid oxygen.

4. The method recited in claim 3, including cooling said removed coke oven gas with water, and cooling the water with liquid carbon dioxide.

5. The method recited in claim 3, including using at least some of said ammonia and some of said liquid carbon dioxide in the making of urea.

6. By-product coal carbonization apparatus comprising a coke oven for reducing coal to coke and having an outlet for coke oven gas, a reactor, means for delivering coke from said oven to the reactor to maintain a bed of coke therein, means for removing most of the tar and ammonia and oil from said gas and then delivering the gas to the reactor, a tar plant that receives said tar removed from said gas and produces coal tar pitch, means for making calcium carbonate, means for delivering said pitch and calcium carbonate to the reactor to desulfurize the coke and gas therein, means for continuously removing the gas from the reactor after it has passed through said coke bed, means for cooling the removed gas, and means for periodically withdrawing a batch of desulfurized coke from the reactor.

7. Apparatus according to claim 6, including waste heat boilers associated with the coke oven and said gas removing means for generating steam, and means for spraying said pitch and calcium carbonate into the reactor by means of said steam.

8. Apparatus according to claim 6, including hopper means beneath the reactor for receiving coke therefrom, valves for periodically admitting coke to and discharging it from said hopper means, water jacketing surrounding said hopper means, and means for circulating a cooling liquid through said jacketing to cool the coke in the hopper means.

9. Apparatus according to claim 6, in which said cokedelivering means include a coke hopper connected with the top of the reactor, the hopper and reactor being surrounded by water jackets, and said apparatus includes a steam chamber, conduits for delivering steam to said chamber from said water jackets, a waste heat boiler associated with the coke oven for generating steam, a conduit connecting the boiler with said chamber, and a conduit connecting said chamber with said delivering means for said pitch and calcium carbonate to spray the pitch and calcium carbonate into the reactor.

10. Apparatus according to claim 6, including an ammonia still, means for water-cooling the coke and thereby generating steam, means for conducting the steam to the ammonia still to heat the still, a reverse osmosis system for processing liquid from said still and discharging water, ammonia scrubbing means, means delivering water from said system to the scrubbing means, means for condensing water vapor from the coke oven combustion gases, and means for supplying the condensed vapor to said scrubbing means as make-up water.

11. Apparatus according to claim 6, including means for delivering steam, substantially pure oxygen and some of said removed coke oven gas to the coke oven to fire the oven and form products of combustion that include carbon dioxide gas and water vapor, means for condensing said vapor and separating it from the carbon dioxide, a carbon dioxide liquefying plant, a liquid oxygen plant, and means for delivering liquid carbon dioxide to the liquid oxygen plant to furnish the refrigeration therefor.

12. Apparatus according to claim 11, in which said means for cooling the coke oven gas include a water circuit and means for cooling the water in said circuit with said liquid carbon dioxide.

13. Apparatus according to claim 1 1, including a urea plant, and means for delivering at least some of said ammonia and some of said liquid carbon dioxide to said urea plant. 

2. The method recited in claim 1, including producing steam by waste heat from said coal heating and by heat removed from said gas in cooling it, and using said steam to spray said tar pitch and calcium carbonate onto said bed.
 3. The method recited in claim 1, including using steam, substantially pure oxygen and some of said removed coke oven gas to produce the heat for the coal and form products of combustion that include carbon dioxide gas and water vapor, condensing said vapor and separating it from the carbon dioxide, liquefying the carbon dioxide, and using liquefied carbon dioxide as a refrigerant in the production of liquid oxygen.
 4. The method recited in claim 3, including cooling said removed coke oven gas with water, and cooling the water with liquid carbon dioxide.
 5. The method recited in claim 3, including using at least some of said ammonia and some of said liquid carbon dioxide in the making of urea.
 6. By-product coal carbonization Apparatus comprising a coke oven for reducing coal to coke and having an outlet for coke oven gas, a reactor, means for delivering coke from said oven to the reactor to maintain a bed of coke therein, means for removing most of the tar and ammonia and oil from said gas and then delivering the gas to the reactor, a tar plant that receives said tar removed from said gas and produces coal tar pitch, means for making calcium carbonate, means for delivering said pitch and calcium carbonate to the reactor to desulfurize the coke and gas therein, means for continuously removing the gas from the reactor after it has passed through said coke bed, means for cooling the removed gas, and means for periodically withdrawing a batch of desulfurized coke from the reactor.
 7. Apparatus according to claim 6, including waste heat boilers associated with the coke oven and said gas removing means for generating steam, and means for spraying said pitch and calcium carbonate into the reactor by means of said steam.
 8. Apparatus according to claim 6, including hopper means beneath the reactor for receiving coke therefrom, valves for periodically admitting coke to and discharging it from said hopper means, water jacketing surrounding said hopper means, and means for circulating a cooling liquid through said jacketing to cool the coke in the hopper means.
 9. Apparatus according to claim 6, in which said coke-delivering means include a coke hopper connected with the top of the reactor, the hopper and reactor being surrounded by water jackets, and said apparatus includes a steam chamber, conduits for delivering steam to said chamber from said water jackets, a waste heat boiler associated with the coke oven for generating steam, a conduit connecting the boiler with said chamber, and a conduit connecting said chamber with said delivering means for said pitch and calcium carbonate to spray the pitch and calcium carbonate into the reactor.
 10. Apparatus according to claim 6, including an ammonia still, means for water-cooling the coke and thereby generating steam, means for conducting the steam to the ammonia still to heat the still, a reverse osmosis system for processing liquid from said still and discharging water, ammonia scrubbing means, means delivering water from said system to the scrubbing means, means for condensing water vapor from the coke oven combustion gases, and means for supplying the condensed vapor to said scrubbing means as make-up water.
 11. Apparatus according to claim 6, including means for delivering steam, substantially pure oxygen and some of said removed coke oven gas to the coke oven to fire the oven and form products of combustion that include carbon dioxide gas and water vapor, means for condensing said vapor and separating it from the carbon dioxide, a carbon dioxide liquefying plant, a liquid oxygen plant, and means for delivering liquid carbon dioxide to the liquid oxygen plant to furnish the refrigeration therefor.
 12. Apparatus according to claim 11, in which said means for cooling the coke oven gas include a water circuit and means for cooling the water in said circuit with said liquid carbon dioxide.
 13. Apparatus according to claim 11, including a urea plant, and means for delivering at least some of said ammonia and some of said liquid carbon dioxide to said urea plant. 